The present invention relates to an illuminated keyboard switch that is used as an input device for various types of electronic equipment, such as a personal computer and a word processor.
As such electronic equipment as personal computers and word processors has come into widespread use recently, keyboard switches used as input devices for such equipment also have more multiple functions. For example, a keyboard switch that allows illumination of such indication as letters, symbols, pictures on a push button is required so that the push button can be identified even in dark environments.
A conventional illuminated keyboard switch is described with reference to FIGS. 13 to 15.
FIG. 13 is a partially sectional view of a conventional illuminated keyboard switch and FIG. 14 is an exploded perspective view thereof. With reference to these drawings, light-conductive milky white indication part 1A for letters, symbols, pictures and the like is formed on push button 1 of insulating resin by such a method as two-color forming.
Cup-shaped elastic member 2 made of rubber or elastomer forces push button 1 upwardly. Reference numeral 3 shows an upper sheet that has travelling contact 3A on the bottom face of a transparent insulating film. Reference numeral 4 shows a lower sheet that has fixed contact 4A on the upper face of an insulating film in a similar manner. Upper sheet 3 and lower sheet 4 are bonded by spacer 5 having adhesive applied to the top and bottom faces thereof, and travelling contact 3A and fixed contact 4A are opposite to each other with a predetermined gap therebetween to form membrane switch 6.
Reference numerals 7 and 8 show first and second arms made of insulating resin, respectively. Reference numeral 9 shows a baseboard made of a copper sheet or aluminum. For first and second arms 7 and 8, the upper ends thereof engage with the bottom face of push button 1, the intermediate portions thereof intersect and pivotally engage with each other in a substantially X-shape, and each of the bottom ends thereof is pivotally supported by baseboard 9.
Reference numeral 10 shows a dust-proof and waterproof protective sheet. Reference numeral 11 shows a wiring board made of such materials as paper/phenol substrate and glass/epoxy substrate. A plurality of wiring patterns (not shown) are formed on the top and bottom faces of wiring board 11, and light-emitting diode (LED) 12 is mounted in a position in the vicinity of the contacts of membrane switch 6. In this manner, an illuminated keyboard switch is constructed.
With the above-mentioned structure, when the top face of push button 1 is pressed in the state shown in FIG. 13, push button 1 is moved downwardly while guided by first and second arms 7 and 8, and thereby elastic member 2 of which top face is pressed by the bottom face of push button 1 is warped.
Next, as shown in the cross-sectional view of FIG. 15, pressing part 2A on the inner surface of elastic member 2 presses and warps upper sheet 3 of membrane switch 6, and travelling contact 3A on the bottom face of upper sheet 3 comes into contact with fixed contact 4A on lower sheet 4.
When the pressing force exerted to push button 1 is released, elasticity restoring force of elastic member 2 moves push button 1 upwardly and restores the button to the state shown in FIG. 13. In this manner, the contacts of membrane switch 6 are brought into and out of contact by pressing operation of push button 1.
Light from light-emitting diode (LED) 12 mounted on wiring board 11 passes through hole 9A formed through baseboard 9 and illuminates indication part 1A for letters, symbols, pictures and the like on push button 1 from the bottom. Thus, push button 1 can be identified even in dark environments.
However, for the above-mentioned conventional illuminated keyboard switch, push button 1 is illuminated using LED 12, which emits strong light in a particular direction. Therefore, illumination is insufficient when indication part 1A is in a position displaced from the light-emitting direction of LED 12 In addition, in the case of keyboard switches, for example, a large number of push buttons 1 are arranged, and thus the number of LEDs 12 required is the same as that of push buttons. This poses problems: an increase in the number of components to be used, more time taken to mount the LEDs on wiring board 11, and thus expensiveness.
The present invention addresses such conventional problems and aims to provide an inexpensive illuminated keyboard switch that allows clear illumination of the push button and uses a smaller number of components.
In order to attain the above-mentioned objects, an illuminated keyboard switch in accordance with the present invention includes:
a push button having an indication part for letters, symbols, and pictures formed thereon;
a cup-shaped elastic member disposed under the push button and forcing the push button upwardly;
a membrane switch disposed under the elastic member; and
an electro-luminescence (EL) element disposed on the top or bottom face of the membrane switch.
The EL element that is a surface light-emitting allows clear illumination of the push button. The EL element can also illuminate a plurality of push buttons at the same time. The use of the EL element can reduce the number of components to be used and thus provide an inexpensive illuminated keyboard switch.